Electrosurgical procedures typically rely on the application of high frequency, for example radio frequency (RF), energy to treat, cut, ablate or coagulate tissue structures such as, for example, neural tissue. One example of a treatment procedure incorporating the application of RF energy to treat neural tissue is lumbar facet denervation. The efficacy of the minimally invasive technique of delivering RF electrical current to neural tissue in lumbar facet denervation has been studied at length and these studies show that this procedure is an effective method of relieving low back pain. The high frequency energy is often delivered to a region of tissue from an energy source such as a generator via a probe that is inserted into a patient's body through an introducer needle. The resistance of tissue, located proximate a conductive region of the probe, to the high frequency energy, causes the tissue temperature to rise. The temperature is generally increased to a sufficient level to coagulate unmyelinated nerve structures, at which point a lesion is formed, resulting in pain relief. The probe is typically a stainless steel electrode that is manufactured to fit within an introducer needle (which may also be referred to as a cannula or tube). Some probes incorporate a temperature sensor to allow for monitoring of temperature throughout the procedure. The temperature can be used to control the delivery of the high frequency energy.
Introducer needles with varying geometries are used in such applications. For example, a tip of the introducer needle can be pointed, blunt and rounded, or open, varying in shape in accordance with the needs of different procedures. Pointed tips allow for penetration of tissue without the need for an external device while rounded tips are useful in soft tissue areas such as the brain where it is critical not to damage nerves. However, it should be noted that blunt introducer needles can do more tissue damage than small-diameter sharp introducer needles. U.S. Pat. No. 6,146,380 to Racz et al. describes introducer needles with curved conductive tips used in high frequency lesioning procedures. An introducer needle typically includes an insulated shaft with an electrically exposed and conductive tip at the distal end of the introducer. A hub at the proximal end of the introducer can also be provided as a connection site for an injection syringe. Introducer needles can therefore be used to inject anesthetic fluid or other treatment compositions, such as therapeutic agents, in addition to playing a role in the insertion of a device into a patient's body and the delivery of electrical energy to a region of tissue.
A typical treatment procedure utilizes an introducer needle having a hollow shaft and a removable stylet therein. This introducer needle is inserted into the patient's body and positioned via imaging technology. Once the introducer needle is positioned, the stylet is withdrawn. The distal end of the probe is then inserted into the shaft of the introducer needle until the distal end of the probe is at least flush with the distal end of the shaft. The probe is connected to a generator that generates electrical current. To ensure that only certain nerves will be treated, a stimulation procedure may be employed. This stimulation involves the delivery of low frequency electrical current in order to excite nerves. This procedure can differentiate between motor and sensory nerves and can confirm that the nerve to be treated is in fact the source of pain.
After placement is confirmed with the stimulation procedure, the probe is withdrawn. A syringe is then attached to the proximal end hub of the introducer needle in order to inject anesthetic fluid or other treatment compositions into the tissue. Following this injection of material, the syringe is removed and the probe is reinserted into the shaft of the introducer needle. Finally, high frequency electrical current is applied from the generator, via the probe and introducer needle, to the tissue adjacent the conductive tip and a lesion is formed. This high frequency electrical current generally returns to the generator through a return (also known as dispersive) electrode typically placed on an exterior surface of the patient's body.
Such a procedure can be used to denervate (that is, to neutralize the ability of neural tissue to convey signals to a patient's brain) specific portions of a patient's spine. Similar procedures may also be applied to other anatomical areas such as intercostal and trigeminal nerves. Accurate placement of the introducer needle's conductive tip in a complicated structure like the spine requires great technical skill by the treating physician. In these procedures, the introducer needle is often viewed via X-ray fluoroscopy, which assists in visualizing the introducer as it's guided into the patient's body.
One limitation of this technique is that placement achieved at the beginning of a procedure can be unintentionally altered by the attachment of a fluid delivery mechanism, for example a syringe, the actuation of the fluid delivery mechanism, or the removal and re-insertion of the probe after the stimulation procedure is complete. For example, to ensure that the fluid being injected does not leak, the fluid delivery mechanism must be tightly secured to the hub of the introducer needle. This twisting or pushing motion applies pressure to the introducer needle thus altering its placement within the body. Also, the probes are generally designed in such a manner that they are only slightly smaller than the inner diameter of the introducer needle to allow for a good electrical connection between the probe and the conductive tip region of the introducer needle. This tight fit requires the application of relatively high insertion forces to align the distal end of the probe with the end of the introducer needle. Therefore when the probe is inserted, removed or reinserted after the injection of a treatment composition, the forces applied can move the introducer needle. Movement caused by any of these inherent procedural complications creates a potential for unpredictable lesion development due to possible repositioning of the probes. The range of distance within which the tip of the introducer needle may move (thus altering the position of the probe) depends on the depth of the needle and the properties of the tissue. The tip may move radially up to 5 mm and axially up to 10 mm. Even slight variations in position can affect the outcome of the procedure. Therefore, placement often relies on the physician to visually monitor the position of the conductive tip throughout the procedure. However, variations in position can be so slight as to go unnoticed by a physician using the imaging technology currently available. Repeating the stimulation procedure to confirm the position of the probe following reinsertion is not viable since anesthetic has already been introduced. Thus, it would be beneficial to have a device or apparatus that would reduce or eliminate the need for those procedural steps that may result in unintentional movement of the introducer needle or probe.
Thus, based on the current state of the art, a need generally exists for an electrosurgical device or apparatus capable of overcoming some or all of the limitations and deficiencies of the prior art.